The present invention relates to a vehicular lamp, and more particularly to a vehicular lamp having an improved air vent structure through which the interior of the lamp housing is communicated with outside air. Particularly, the invention provides a vehicular lamp in which such an air vent structure can be produced in a reduced size and the airtightness of the lamp housing can easily be tested.
A vehicular lamp is provided with an air vent structure in order to equalize any differences in pressure between the interior lamp housing and the atmosphere caused, for instance, by a temperature rise inside the lamp housing when the lamp is lit or by a temperature drop when the lamp is extinguished.
FIG. 15 shows an example of a conventional air vent structure. In FIG. 15, a designates a lamp body from which a pipe b integrally projects The rear portion of the pipe b is bent downward so that the pipe has a laterally-directed L-like shape in side view.
FIG. 16 shows another example of an air vent structure used in the prior art. In this example, a pipe d projects rearward from a lamp body c in a straight manner. The upper end of a waterproof tube e, which has a laterally-directed U-like shape in side view, is fitted onto the rear end of the pipe d.
However, the lamp shown in FIG. 15 has problems in that slide molds are required in the molding process used to produce the lamp body, and that it is difficult to test the airtightness of the lamp apparatus.
The above problems will be described more specifically. Assuming that the molds for the lamp body a open in forward and rearward directions, since the pipe has an L-like shape, a core which slides in a direction perpendicular to the mold opening direction must be used in the process used for molding the pipe b. This makes the molds complicated in structure, and hence causes the production cost to be increased.
In order to test for airtightness, all openings in the lamp body must be closed, other than the opening through which air for pressurizing the interior of the lamp housing (usually the bulb mounting hole is used for this purpose). In the lamp shown in FIG. 15, the pipe b opens downward. Therefore, a member for closing the opening of the pipe must be firmly fitted into the opening from underneath, thereby producing a problem in that such an operation is difficult to perform. Particularly, the fact that the work of closing the opening of the pipe b cannot be conducted from directly behind the lamp makes automatization of the airtightness test very difficult.
In the vehicular lamp shown in FIG. 16, a waterproof tube e having a complicated structure is required, and hence the number of parts is increased. Furthermore, the waterproof tube e has a laterally-directed U-like shape in side view. This produces a problem in that, when the tube is attached to the pipe d, the resulting air vent structure has overall a large size.